Rate Transient Analysis, or RTA, is the natural complement to Pressure Transient Analysis (PTA) when one has pressure and rate data.# RTA can be used to increase the area of investigation when compared to using PTA alone. Advancements in RTA have progressed partly due to the development of permanent downhole pressure gauges. Users are able to obtain answers that were previously only available from PTA. The advantage is that information is available at no extra cost as there is no deferred production. RTA started in the 1920s on a purely empirical basis, and as a financial tool however it has now evolved to a modern methodology that shares a lot of analysis and modeling tools with PTA. The long-term production can be modeled and forecasting is based on real models as opposed to an empirical function. Topaze NL is fully compatible with Saphir NL data and models. An extensive analytical model catalog and numerical capability provides reliable history matching and forecasting.